@article{MOMA_1978__86_177884,
     author = {Frank Piefke},
     title = {Ma{\ss}e f\"ur gerichtete {Geraden} und nicht-symmetrische {Pseudometriken} in der {Ebene.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {143--154},
     publisher = {mathdoc},
     volume = {86},
     year = {1978},
     zbl = {0371.60018},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1978__86_177884/}
}